Mikio Yamanouchi

Equilibrium charge fractions of ions of Z = 4–92 emerging from a carbon foil

Based on recent findings that the variation of charge fractions, mean charges, and charge distribution widths with ion energy E and projectile atomic number Z is strongly dependent on the shell structure of the ions, systematic reanalysis of the charge distributions of ions has been performed. Graphs are presented for equilibrium charge fractions thus obtained of ions emerging from a carbon foil as a function of exiting ion energy E ranging from 0.02 to 6 MeV/u. Each graph pertains to one ion species from Z = 4 to 83 and Z = 92. Tables of the mean charges and charge distribution widths are also given for each ion species in the same range of Z and E. Charge fractions of fully stripped ions, H-like ions, and He-like ions are also tabulated from Z = 4 to 20 for fast ions with E up to 40 MeV/u.

Equilibrium charge state distributions of fast Si and Cl ions in carbon and gold foils

Abstract Equilibrium charge state distributions have been measured for 30–110 MeV Si ions in carbon and gold foils and 25–142 MeV Cl ions in carbon foils. Obtained values of mean charge states have been well reproduced by the empirical formula by Shima et al. in both ion energy dependence and foil Z 2 dependence. Asymmetric charge state distributions are in fairly good agreement with the prediction of the chi-squared model by Baudinet-Robinet.

Statistical Yrast line effect in 16O + 27Al and 19F + 24Mg fusion cross sections

Abstract In measurements of the fusion cross sections of the systems 16 O + 27 Al and 19 F + 24 Mg in the energy range of 43 Sc ∗ , 40 MeV ≲ E ∗ ≲ 80 MeV , it has been observed that the Z -distributions of the evaporation residues and the extracted critical angular momenta are the same for the two entrance channels. These features confirm that the fusion cross sections at relatively high energies are rather determined by the properties of the compound nucleus like the “statistical yrast line”.

PHOTOPROTONS FROM FLUORINE AND CARBON

The (γ, p ) reactions in fluorine and carbon were studied with bremsstrahlung X-rays of energies up to 24 MeV. Photoprotons were observed by using nuclear plates. Energy spectrum of photoprotons from fluorine exhibits peaks at 3.8, 4.6, and 7.4 MeV which are in good accord with those observed previously by Forkman and Wahlstrom, and Dodge and Barber. In addition to these we found peaks at 1.9 and 2.8 and a somewhat uncertain peak at 6.1 MeV. Angular distributions of photoprotons from fluorine showed an asymmetry around 90° with respect to the direction of incident photons, which suggests interference between absorbed photons of different parities. In the case of carbon, a main peak at proton energy of 6.0 MeV was observed along with slight humps at 4.5 and 5.2 MeV. The observed structure is in good agreement with those reported previously.

The 12 UD pelletron accelerator at the University of Tsukuba

Abstract The 12 UD Pelletron installed at the Tandem Accelerator Center of the University of Tsukuba has been in operation for nearly four years. The installation of the accelerator is described and the operational experience with the accelerator and associate facilities are summarized.

A new version of sputter ion source utilizing an ionizer of platinum plate

A sputter ion source, TUNIS (Tsukuba Universal Negative Ion Source), has been developed. TUNIS consists of a cesium ion source and a sputter cone assembly which is similar to that of Middleton. The cesium ion source has a special feature in that it utilizes a front-feed type cesium ionizer to produce bombarding cesium ions. TUNIS has been proved to be competent for producing a good deal of ion beams which are acceptable to the 12 UD Pelletron accelerator of the University of Tsukuba. Operating conditions of TUNIS as well as the performance of the cesium ionizer are presented.

Radiative Electron Capture (REC) as an Indicator of the K-Vacancy State of Highly Ionized Projectiles in Solids: Application to Stopping Power

Radiative electron capture (REC) has been studied at the Tandem Accelerator Center,Tsukuba University. The NEC 12 UD tandem and sputter ion source provided na beams of Clq+ ranging from 17+, 16+, 10+, 8+ and 7+ at energies of 120,95 and 80-MeV which were incident on C targets of varying thickness. The object of this work was to extend to higher energies and charge states the REC target thickness studies which had been done at TUNL. In this report the data on REC cross sections, centroid energies and widths vs. target thickness are given and discussed qualitatively. The relevance of such studies to target thickness dependence of stopping power is demonstrated.

Target thickness dependence of Kα X-ray energy shifts in 80 and 120 MeV Cu + Cu collisions

Abstract Energy shifts of target Kα x-rays in 80 and 120 MeV Cu + Cu collisions have been observed to vary 90–108 and 100–137 eV, respectively, in target thicknesses of 1–20 μg/cm2 range where the projectile charge states change from nonequilibrium to equilibrium.

Study of the Excited States of 4He through the 4He(γ, p) 3H Reaction

Proton spectra from the 4 He(γ, p ) 3 H reaction with 32 MeV bremsstrahlung X-rays were measured at 45°, 90° and 135° lab angles. Two broad peaks were found at 24 and 27 MeV, and a local minimum at 26 MeV in the excitation function. The sin 2 θ angular distribution at the two peaks suggests that the reaction proceeds mainly through E1 absorption. An analysis of the data in terms of two non-interfering resonances shows that the lower 1 - T =1 state at 25 MeV in 4 He is mainly a 1 P 1 configuration.

Charge states of fast Cu ions in solids

Abstract The mean number of projectile L-shell electrons inside the foil, the projectile X-ray spectrum and the equilibrium charge distribution outside the foil have been measured for 1 and 2 MeV/u Cu ions. Projectile charge states outside the foil as well as their excited states inside the foil differ with respect to the foil species. The relationship of the projectile charge states between outside and inside the foil is discussed for ions whose L- and M-shell electrons are mainly involved in a charge exchange process during the collision.